A storage system typically comprises one or more storage devices into which information may be entered, and from which information may be obtained, as desired. The storage system includes a storage operating system that functionally organizes the system by, inter alia, invoking storage operations in support of a storage service implemented by the system. The storage system may be implemented in accordance with a variety of storage architectures including, but not limited to, a network-attached storage environment, a storage area network and a disk assembly directly attached to a host computer. The storage devices are typically disk drives organized as a disk array, wherein the term “disk” commonly describes a self-contained rotating magnetic media storage device. The term disk in this context is synonymous with hard disk drive (HDD) or direct access storage device (DASD). The storage operating system of the storage system may implement a high-level module, such as a file system, to logically organize the information stored on volumes as a hierarchical structure of storage objects, such as files and logical units (LUs). A known type of file system is a write-anywhere file system that does not overwrite data on disks.
The storage system may be further configured to allow many servers to access storage objects stored on the storage system. In this model, the server may execute an application, such as a database application, that “connects” to the storage system over a computer network, such as a point-to-point link, shared local area network (LAN), wide area network (WAN), or virtual private network (VPN) implemented over a public network such as the Internet. Each server may request the data services of the storage system by issuing access requests (read/write requests) as file-based and block-based protocol messages (in the form of packets) to the system over the network.
A plurality of storage systems may be interconnected as a cluster to provide a storage system architecture configured to service many servers. In some embodiments, the storage system architecture provides one or more aggregates, each aggregate comprising a set of one or more storage devices (e.g., disks). Each aggregate may store one or more storage objects, such as one or more volumes. An aggregate may be distributed across a plurality of storage systems. The storage objects (e.g., volumes) may be configured to store content of storage objects, such as files and logical units, served by the cluster in response to multi-protocol data access requests issued by servers.
Each storage system of the cluster may include (i) a storage server (referred to as a “D-blade”) adapted to service a particular aggregate or volume and (ii) a multi-protocol engine (referred to as an “N-blade”) adapted to redirect the data access requests to any storage server of the cluster. In the illustrative embodiment, the storage server of each storage system is embodied as a disk element (D-blade) and the multi-protocol engine is embodied as a network element (N-blade). The N-blade receives a multi-protocol data access request from a server, converts that access request into a cluster fabric (CF) message and redirects the message to an appropriate D-blade of the cluster.
The storage systems of the cluster may be configured to communicate with one another to act collectively to increase performance or to offset any single storage system failure within the cluster. The cluster provides data service to servers by providing access to a shared storage (comprising a set of storage devices). Typically, servers will connect with a storage system of the cluster for data-access sessions with the storage system. During a data-access session with a storage system, a server may submit access requests (read/write requests) that are received and performed by the storage system.
Each server typically executes numerous applications requiring the data services of the cluster. For example, data for a particular application may be stored as a dataset on a particular storage system of the cluster. The dataset may comprise a plurality of storage objects (e.g., volumes) stored on the storage system. The particular application may access its dataset on the storage system to add, modify, or delete data of the dataset. In addition, the storage system may provide a backup data service that produces a backup image of an application's dataset. The backup image of a dataset may be used for example, to restore the dataset in case of data corruption of the dataset.
In current cluster storage systems, however, it is becoming more common for a dataset of an application to comprise a plurality of storage objects that are stored across a plurality of different storage systems. In this situation, it has become more difficult to produce a successful overall image of a dataset stored across many storage systems. In particular, conventionally it is difficult to coordinate and ensure that all storage systems have successfully produced their images and have not retained stale backup images from failed backup attempts. As such, an effective method for managing and producing an image for a dataset stored across multiple storage systems is needed.